Figure captions
Figure 1 Landscape site at Damxung County on the central Tibetan Plateau and the pictures of the alpine steppes encroached (a) by a leguminous shrub (Caragana spinifera ) and (b) by an none-leguminous shrub (Dasiphora fruticosa ).
Figure 2 Differences in (a) vegetation cover (Cover), (b) plant height (Height), (c) species richness (SR), (d) aboveground biomass (AGB), (e) belowground biomass (BGB), (f) soil water content (SW), (g) soil organic carbon content (SOC), (h) soil total nitrogen content (STN), (i) soil microbial biomass carbon (MBC), (j) soil microbial biomass nitrogen (MBN), (k) soil ammonia nitrogen (NH4+−N), and (l) soil nitrate nitrogen (NO3−N) for the alpine steppes encroached by a leguminous shrub (Caragana spinifera ) and by an none-leguminous shrub (Dasiphora fruticosa ). Mean ± SD is shown in error bars. Asterisks represent the significant differences between the shrub encroached plots and non-shrub encroached plots. *p < 0.05; ** p < 0.01; *** p< 0.001.
Figure 3 Differences in the relative interaction intensity (RII) values of individual ecosystem functions for the alpine steppes encroached by (a) a leguminous shrub (Caragana spinifera ) and (b) by an none-leguminous shrub (Dasiphora fruticosa ). Cover, vegetation cover; Height, plant height; SR, species richness; AGB, aboveground biomass; BGB, belowground biomass; SW, soil water content; SOC, soil organic carbon content; STN, soil total nitrogen content; MBC, soil microbial biomass carbon; MBN, soil microbial biomass nitrogen; NH4+−N, soil ammonia nitrogen; NO3−N, soil nitrate nitrogen. Bars indicated the SD of mean value. Asterisks represent the significant differences between the shrub encroached plots and non-shrub encroached plots. * p < 0.05; ** p < 0.01; ***p < 0.001.
Figure 4 Differences in (a) the ecosystem multifunctionality (EMF), (b) aboveground ecosystem multifunctionality (AEMF), (c) belowground ecosystem multifunctionality (BEMF) indexes between the shrub encroached plots and non-shrub encroached plots and the relative interaction intensity (RII) values of EMF, AEMF, and BEMF for the alpine steppes encroached by (e) a leguminous shrub (Caragana spinifera ) and (f) by an none-leguminous shrub (Dasiphora fruticosa ). Bars indicated the SD of mean value. Asterisks represent the significant differences between the shrub encroached plots and non-shrub encroached plots. * p < 0.05; ** p < 0.01; ***p < 0.001.
Figure 5 Correlation coefficients among the individual ecosystem functions and multiple ecosystem functions relevant to the ecosystem multifunctionality (EMF), aboveground ecosystem multifunctionality (AEMF), belowground ecosystem multifunctionality (BEMF) in the semi-arid alpine steppes. Cover, vegetation cover; Height, plant height; SR, species richness; AGB, aboveground biomass; BGB, belowground biomass; SW, soil water content; SOC, soil organic carbon content; STN, soil total nitrogen content; MBC, soil microbial biomass carbon; MBN, soil microbial biomass nitrogen; NH4+−N, soil ammonia nitrogen; NO3−N, soil nitrate nitrogen. Bars indicated the SD of mean value. Asterisks represent the significant differences between the shrub encroached plots and non-shrub encroached plots. * p < 0.05; ** p < 0.01; ***p < 0.001.
Figure 6 Correlation coefficients among the relative interaction intensity (RII) values of individual ecosystem functions and multiple ecosystem functions relevant to the ecosystem multifunctionality (EMF), aboveground ecosystem multifunctionality (AEMF), belowground ecosystem multifunctionality (BEMF) in respond to shrub encroachment. Cover, vegetation cover; Height, plant height; SR, species richness; AGB, aboveground biomass; BGB, belowground biomass; SW, soil water content; SOC, soil organic carbon content; STN, soil total nitrogen content; MBC, soil microbial biomass carbon; MBN, soil microbial biomass nitrogen; NH4+−N, soil ammonia nitrogen; NO3−N, soil nitrate nitrogen. Bars indicated the SD of mean value. Asterisks represent the significant differences between the shrub encroached plots and non-shrub encroached plots. * p < 0.05; ** p< 0.01; *** p < 0.001.
Figure 7 A schematic diagram for understanding the potential ways of shrub encroachment on the individual ecosystem functions and multiple ecosystem functions in the semi-arid alpine steppes.